Process for spinning a high viscosity, high gamma viscose



United States Patent PRGfiESS FUR PINNXNG A HIGH VISCUSKTY,

HIGH GAMMA VISCQfiE Yoshikazu Aolri, Gtsu, and Teruii Kamei, Sakyo-hn,

Kyoto, Japan, assignors to Tachikawa Research Institute, Higashiyama-hn, Kyoto, .iapan, a corporation of Japan No Drawing. Filed June 27, 11962, Ser. No. 205,565

5 Claims. (Cl. 264-188) This invention relates to a process for producing rayon as regenerated cellulose in the form of filaments or fibers. In particular, it is concerned with an improved method for regenerating cellulose by the spinning of viscose in the manufacture of viscose rayon yarn. This is a continuation-impart of application Serial No. 64,730, now abandoned, filed October 25, 1960.

The basic process contemplated by this invention essentially entails the spinning of tin-ripened viscose in a low acid concentration bath, the temperature of the bath being controlled and the viscose having a high degree of polymerization. Processes of this type are known to the art being described, for example, in US. Patents Nos. 2,592,355, 2,732,279 and 2,607,955. These processes have proved dissatisfactory from the standpoint that the spinning velocity may not be increased beyond a certain limit without seriously diminishing the tenacity of the resulting filament or fiber and jeopardizing the stability of the process itself due to actual breakage of the semi-coagulated viscose thread Within the bath or outside thereof as it is being reeled onto the stretching or tension imparting components. Thus far, it has been found that for high viscosity viscose a spinning velocity of 20 meters per minute is about the permissible maximum in commercial practice and this relatively low velocity has been considered a disadvantage.

The inventive concept herein is directed toward the solution of the problem of spinning viscose which has a hgh degree of polymerization. That the problem is significant is due to the fact that the higher the degree of polymerization of the spun fiber, the more nearly will it have the intrinsic properties of natural fiber. As pointed out in Patent No. 2,732,279, it had been thought that an essential condition of spinning high DP. viscose is to keep the bath temperature below 30 C. This requirement was due to the unduly high rate of regener-ation of the viscose rayon fiber at higher temperatures which adversely aliected the strength of the regenerating filaments. However, the relatively low bath temperature limits the permissible spinning velocity. According to the instant process, the high DP. viscose is spun in a coagulating bath the temperature of which is raised above 30 C. which, as is well known, enables higher spinning velocities. Concomitantly, however, the nature and percentage composition of the bath is maintained within critical limits and also in critical relation to the temperature so as to permit the raised temperature without the resulting adverse effect thereof.

The present invention envisions, therefore, a spinning process in which high D.P. viscose is spun at 30 meters per minute or more and which is adapted to produce filaments or fibers with superior properties. The sulphuric acid concentration in the bath is low, for example, within the range of 1 to 30 grams :per liter and the initial material is unripened viscose having a high viscosity or degree of polymerization. A weak acid bath is hereby defined as one in which the acid concentration is within the approximate limits stated above and high viscosity cellulose has a viscosity above 250. In addition, the gamma value of the viscose is above 50 and preferably between 50 and 100. Principal features of the invention relate to such factors as temperature of the spinning bath and zinc sulphate concentration and are directly productive of the desired higher spinning velocity and stability of the spinning process as an operation as well as improvement in the characteristics of the resulting fibers. In order for these improvements to be obtained, it is required that the temperature of the spinning bath be not less than 30 centigrade and the ZnSO, concentration be within the range of from 0.2 to 2.0 grams per liter. Moreover, it was found that permissible spinning velocity and bath temperature over 30 centigrade can be directly related provided the bath contains the necessary controlled amount of ZnSO In conventional processes which do not provide ZnSO in the bath the regeneration of the viscose rayon fiber proceeds so rapidly that its strength is not sufiicient to withstand the friction from movement of the spinning liquor at the higher spinning velocities. This is due to the fact that the thread cannot be sufiiciently stretched when regeneration occurs rapidly. It is the function of the ZnSO in controlled amounts to slow the regeneration process or the decomposition of the viscose as measured by its 'y-value so that stretching can occur smoothly and as long as regeneration occurs. The stretching may be eifected by means of special 'godets such as are described and illustrated in U.S. Patent No. 2,732,279. As the condition of the viscose changes from a -value to say 30 to a state where the viscose has completely decomposed and its 'y-value is, therefore, 0, a substantial amount of stretching is possible either inside or outside the bath provided the change in state of the material is controlled which is the function of the ZnSO Under these stipulated conditions, the thread can, in fact, be stretched more than 200% which will assure sufficient tenacity of the coagulating fiber to allow a marked increase in spinning velocity.

The following relation between temperature of the spinning bath and concentraton of ZnSO which are the key factors in the improved spinning process, and spinning velocity have been observed.

Concentration Favorable Spin- Temperature of the spinning bath of ZnSOq, ning Velocity,

centigrade Grams per Meters per Liter Minute Example 1 Wood pulp with a degree of polymerization of 850 is steeped one hour at 20 centigrade in 18% NaOI-I solution, and after being pressed to 2.6 times the weight of the original pulp, it is crushed at 18 Centigrade for 2 hours. Alkali-cellulose without aging, is subjected to xanthation with 45% CS to the weight of the cellulose at 19-28" centigrade for 2.5 hours. The composition of the resulting viscous is 5% cellulose and 3.5% NaOH. This viscose is filtered, deaerated and spun as soon as possible after xanthation, its viscosity (by falling ball method) being 250 and its 'y-value 60. The spinning conditions are as follows: H 80 concentration in the spinning bath is 8.0 grams per liter, ZnSO concentration in the bath is 0.5 gram per liter, temperature of the bath is 35 centigrade, and the thread is stretched to 210% by a godet located outside of the bath, and the final spinning velocity is 40 meters per minute. Characteristics of filament are: 1.4 denier, dry tenacity 4.3 grams per denier, wet tenacity 3.2 grams per denier, dry elongation 12.7%, wet elongation 13.5%, dry knot tenacity 2.1 grams per denier, fiex cycle 650.

Example 2 Linter pulp with degree of polymerization of 1650 is steeped in 19% NaOH solution for 2 hours at 20 centigrade and after being pressed to 2.8 times of the weight of pulp, it is disintegrated for 2.5 hours at 31 centigrade. Without aging, the alkali-cellulose is xanthated with CS in the amount of 60% to the weight of the cellulose for 3 hours at 20-33 centigrade. The composition of the viscose thus obtained is 4.5% cellulose and 4.5% NaOH, its viscosity being 450 and its -value 80. The spinning is carried out in a spinning bath containing 5.4 grams per liter H SO 1.0 gram per liter ZnSO, and at a bath temperature of 40 centigrade. The spinning velocity is 45 meters per minute. The thread, after traveling 15 cm. in the bath, is stretched to 250% by a godet immersed in the spinning bath. The characteristics of the resulting fiber are: 1.0 denier, dry tenacity 5.5 grams per denier, wet tenacity 4.2 grams per denier, dry elongation 12.4%, wet elongation 16.5%, dry knot tenacity 2.4 grams per denier, flex cycle 1100.

Example 3 Wood pulp with a degree of polymerization of 1270 is steeped for 2 hours at 20 C. in 19.0% NaOI-I solution, and after being pressed 2.8 times the weight of the original pulp, it is crushed at 24 for 2 hours. Alkalicellulose, thus obtained, is subjected to xanthation with 55% CS to the weight of the cellulose at 20-28 C. for 2.5 hours. The composition of the resulting viscose is 4.5% cellulose and 3.8% NaOH. After being filtered and deaerated, this viscose is spun, its viscosity (by falling ball method) being 750 and its 'y-value 100. The spinning conditions are as follows: H 80 concentration in the spinning bath is 9.2 grams per liter, ZnSO, concentration in the bath is 0.2 gram per liter, temperature of the bath is 30 C., and the thread of 1,000 filaments is stretched by a godet, and the final velocity is 35 meters per minute.

The characteristics of the resulting fibers are: 1.2 denier, dry tenacity 5 grams per denier, wet tenacity 4 grams per denier, dry elongation 13%, wetelongation 16%, dry knot tenacity 2.1 grams per denier.

Example 4 Wood pulp with a degree of polymerization of 1,100 is steeped for 2 hours at 20 C. in 18.5% NaOI-I solution, and after being pressed 2.8 times the weight of the original pulp, it is crushed at 27 C. for 2.5 hours, alkalicellulose, thus obtained, is subjected to xanthation with 50% CS to the weight of the cellulose at 1927 C. for 2.5 hours. The composition of the resulting viscose is 5.2% cellulose and 3.6% NaOH. After being filtered and reaerated, this viscose is spun, its viscosity being 610 and its 'y-value 85. The spinning conditions are as follows: H SO concentration in the spinning bath is 15.6 grams per liter, ZnSO concentration in the bath is 0.5 gram per liter, temperature of the bath is 35 C., and the thread of 6,000 filaments is stretched by a godet, and the final spinning velocity is 40 meters per minute.

The characteristics of the resulting fibers are: 1.5 denier, dry tenacity 4.8 grams per denier, wet tenacity 3.6 grams per denier, dry elongation 12%, wet elongation 15%, dry knot tenacity 1.8 grams per denier.

4 Example 5 Wood pulp with a degree of polymerization of 950 is steeped for 2 hours at 20 C. in 18.2% NaOH solution, and after being pressed 2.9 times the weight of the original pulp, it is crushed at 28 C. for 2.5 hours, alkali-cellulose, thus obtained, is subjected to xanthation with 45% CS to the weight of the cellulose at 1826 C. for 2.5 hours. The composition of the resulting viscose is 5.5% cellulose and 3.3% NaOH. After being filtered and deaerated, this viscose is spun, its viscosity being 520 and its 'y-value 75. The spinning conditions are as follows: H SO concentration in the spinning bath is 30.0 grams per liter, ZnSO concentration in the bath is 1.2 grams per liter, temperature of the bath is 50 C., and the thread of 18,000 filaments is stretched by a godet, and the final spinning velocity is 50 meters per minute.

The characteristics of the resulting fibers are: 1.5 denier, dry tenacity 4.5 grams per denier, wet tenacity 3.2 grams per denier, dry elongation 11%, wet elongation 14%, dry knot tenacity 1.6 grams per denier.

As mentioned above, the complete absence of the ZnSO in the spinning bath precludes the possibility of imparting sufiicient stretch to the coagulating material to permit of high velocity spinning. On the other hand too much ZnSO in the bath which has a low acid concentration and low temperature causes the formation of the zinc xanthate to become too irregular which also results in the formation of a thread of low tenacity which cannot be spun with higher than conventional spinning velocities.

Various modifications in the process as above described may be effected by persons skilled in the art without departing from the principle and scope of invention as defined in the appended claims.

What is claimed is:

1. In the process for the manufacture of rayon filament or fiber in a weak sulphuric acid bath from viscose, the steps of extruding unripe viscose having a gamma value above 50 into the bath having a ZnSO concentration which varies with the temperature of the bath from 0.2 gram per liter ZnSO concentration for a temperature of 30 centigrade to 2.0 grams per liter ZnSO concentration for a temperature of 50 centigrade.

2. In the process for the manufacture of rayon filament or fiber in a weak acid bath from viscose, the steps if extruding unripe viscose having a gamma value above 50 intothe bath having a sulphuric acid concentration of from approximately 1 to 30 grams per liter and a ZnSO concentration which varies with the temperature of the bath from 0.2 gram per liter ZnSO concentration for a temperature of 30 centigrade to 2.0 grams per liter ZnSO concentration for a temperature of 50 centigrade.

3. In the process for the manufacture of rayon filament or fiber in a weak sulphuric acid bath from viscose, the steps of extruding unripe viscose having a gamma value above 50 into the bath having a ZnSO concentration which varies with the temperature of the bath from 0.2 to 0.5 gram per liter ZnSO for a temperature of 30 centigrade, to 0.4 to 0.7 gram per liter ZnSO for a temperature range of 35 to 40 centigrade, to 0.5 to 2.0 grams per liter ZnSO for a temperature of 50 centigrade.

4. In the process for the manufacture of rayon filament or fiber in a weak acid bath from viscose, the steps of extruding viscose having a viscosity above 250 and a gamma value above 50 into the bath having a sulphuric acid concentration of from approximately 1 to 30 grams per liter and a ZnSO concentration which varies with the temperature of the bath from 0.2 to 0.5 gram per liter ZnSO for a temperature of 30 centigrade, to 0.4 to 0.7 gram per liter ZnSO for a temperature range of 35 to 40 centigrade, to 0.5 to 2.0 grams per liter ZnSO for a temperature of 5 0 centigrade.

5 In the process for the manufacture of rayon filament or fiber in a weak acid bath from viscose, the steps of extruding viscose having a viscosity above 250 and a gamma value above 50 into the bath having a sulphuric acid concentration of from approximately 1 to grams per liter, a ZnSO concentration which varies with the temperature of the bath from 0.2 to 0.5 gram per liter ZnSO; for a temperature of 30 Centigrade, to 0.4 to 0.7 gram per liter ZnSO for a temperature range of to Centigrade, to 0.5 to 2.0 grams per liter ZnSO for a temperature of centigrade, the permissible spinning velocity being 35 meters per minute at 30 centigrade, to 40 meters per minute at 35 to 40 centigrade, to =50 meters per minute at 50 Centigrade.

6 References Cited in the file of this patent UNITED STATES PATENTS 2,307,864 1/43 Soukup 264l88 2,607,955 8/52 Drische et al. 264181 OTHER REFERENCES 1954, Cellulose and Cellulose Derivatives, Part II, edited by Ott et al., 2nd edition, published by Interscience Publishers, Inc., New York.

ALEXANDER H. BRODMERKEL, Primary Examiner.

MICHAEL V. BRINIDISI, MORRIS LIEBMAN,

Examiners. 

1. IN THE PROCESS FOR THE MANUFACTURE OF RAYON FILAMENT OR FIBER IN A WEAK SULPHURIC ACID BATH FROM VISCOSE, THE STEPS OF EXTRUDING UNRIPE VISCOSE HAVING A GAMMA VALUE ABOVE 50 INTO THE BATH HAVING A ZNSO4 CONCENTRATION WHICH VARIES WITH TEH TEMPERATURE OF THE BATH FROM 0.2 GRAM PER LITER ZNSO4 CONCENTRATION FOR A TEMPERATURE OF 30* CENTIGRADE TO 2.0 GRAMS PER LITER ZNSO4 CONCENTRARION FOR A TEMPERATURE OF 50* CENTIGRADE. 